As a conventional exclusive access controlling technique for electronic information, there has been known one for conducting an exclusive access control by a semaphore parameter as disclosed in Japanese Unexamined Patent Publication No. 4-127261. This technique utilizes the semaphore parameter as a flag indicating a used/unused status of electronic information, to thereby realize the exclusive access control for electronic information.
However, the exclusive access control based on only the used/unused status causes a problem in that the access to electronic information is possible at any time, insofar as the electronic information is unused. For example, in case of substantially simultaneous updating requests from two clients for electronic information on a server, it may happen that the electronic information is updated in response to the updating request from one of the clients and thereafter further updated in response to the updating request from the other client. Thus, the updating request from the one client may be perfectly nullified, resulting in deterioration of the stability and reliability of the electronic information.
To avoid such a defect, it is conceivable to conduct an exclusive access control, taking account of the version number of the electronic information. However, in the prior art, since a process for version management is needed to be conducted separately, this renders the process for the exclusive access control redundant.
The present invention has been carried out in view of the conventional problems as described above, and it is therefore an object of the present invention to provide a technique for realizing an exclusive access control having higher reliability with a simple constitution, by utilizing a version number of electronic information, as a part of a semaphore parameter.